1 Field of the Invention
The present invention relates to a method of feeding bivalves. In particular, this invention relates to an arthropod chitin-based diet for bivalves.
2. Description of Related Art
Bivalves in their native environment rely on suspended organic particles including phytoplankton and organic debris for their food. It is known that bivalves have digestive enzymes for digesting protein, lipids, carbohydrates and other food material found in their environment. It has recently been discovered that bivalves also possess enzymes such as chitinase and chitobiase, giving them a high capacity for digesting chitin, a polysaccharide found in phytoplankton, fungi, and many invertebrates. The basic monomer unit of chitin, N-acetyl-D-flucosamine (GlcNAc) is a substance capable of supplying acetate and glucose for energy metabolism and compound synthesis and can be used as a source of amino nitrogen. Moreover, GlcNAc is a key component in the biosynthesis of the organic phase of shell and gill arch development. Thus, chitin may be especially valuable during the early life and juvenile stages of bivalves.
The use of comminuted chitin-containing material periodically added to a body of water as a feed for bivalves and particularly, the use of comminuted arthropod exoskeletons has not been previously reported.
R. A. Smucker and D. A. Wright, Comp. Biochem. Physiol. A., 77A: 239-241 discuss an experiment for determining the presence and activity of chitinase in Crassostrea virginica wherein adult oysters were treated with purified, regenerated chitin (prepared by reacetylation of chitosan) for a period of 72 hours after which the styles were removed and analyzed for chitinase activity and protein content. The study concluded that chitinase is an integral component of the oyster digestive system, allowing oysters to make use of the chitin present in their natural diet.
Mayasich, S. A. and R. A. Smucker, Microb. Ecol. 14: 157-166 (1987) discuss an experiment wherein oysters were treated with colloidal, regenerated chitin for a 24 hour period after which their styles were removed and analyzed.
U.S. Pat. No. 3,298,354 to Geer discloses a method of enhancing the growth of the shells of bivalve larvae by mixing into their water a dust made from the shell of the particular bivalve.
U.S. Pat. No. 3,592,168 to Claus discloses a method of feeding bivalves separated blood cells. The patent discloses that the ideal size range for bivalve foods is from 4 to 20 micron diameter.
U.S. Pat. No. 4,080,930 to Pruder et al. discloses a method of growing marine bivalves including feeding them a diet of algae.
U.S. Pat. No. 3,196,833 to Glancy discloses a method of producing shellfish seed in a contaminant free and nutrient including environment.
U.S. Pat. No. 3,870,020 to Hunt discloses a method of growing oysters in a controlled environment with the diatom Cyclotella nana used as the food source for the oysters.
U.S. Pat. No. 1,933,950 to Wells discloses a method of shellfish culture including centrifuging the culture water to remove bodies larger than the shellfish.
U.S. Pat. No. 4,449,480 to Ison et al. discloses a method of transforming glochidia larvae of freshwater mussels to the juvenile stage that includes feeding the larvae a complex artificial growth medium containing antibiotics, antimycotics, inorganic salts, amino acids, vitamins, and other compounds including glucose.
Current methods commonly used for feeding bivalves include raising the bivalves in an environment of natural, filtered or centrifuged sea water, alone or with the addition of phytoplankton or concentrated formulated foods containing protein, fat and carbohydrates. The disadvantages of the use of phytoplankton and formulated foods include their great expense. It has been calculated that phytoplankton production costs represent more than 30% of juvenile oyster production costs. Phytoplankton production is keyed to natural seasonal cycles and is limited primarily by insolation and temperature.